Fiber and corrugated metal mat support
The present invention discloses a support for securely holding an exhaust catalyst in a combustion and exhaust system. The support of the invention includes a flexible refractory mat adapted to surround the exhaust catalyst and a metal foil having a plurality of protrusions disposed over the flexible refractory mat. The present invention also discloses an exhaust system in which a catalyst is held in place with the support of the invention. Finally, methods for securing a catalyst to an exhaust system are provided.
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1. Field of the Invention
In at least one aspect, the present invention provides an improved support for a catalyst placed within an exhaust system.
2. Background Art
Virtually every modern automobile contains an exhaust system for removing various environmentally harmful byproducts of an internal combustion engine. Also, many combustion furnaces, and electrical generators use catalytic convertors. Typically, various catalysts are used to accomplish this removal. These catalysts are exposed to a wide range of temperatures from below freezing up to several hundred degrees Fahrenheit. An important requirement in the design of exhaust systems is the mounting of a support of the catalyst. The material selection for these support systems must securely hold the catalyst in place at all temperatures to which the catalyst is exposed.
Several methods exist for supporting exhaust catalysts in an exhaust system. For example, knitted wire mesh supports or mat supports have been used to securely hold exhaust catalysts in place. The knitted wire mesh support has a lower maximum use temperature and a lower thermal insulating value. Moreover, knitted wire mesh supports tend to be expensive. Therefore, it is only used for applications where the temperature is so low and the use of mat is precluded.
Mat supports are ideal from many standpoints except cold holding ability. Such mat supports often contain a vermiculite popping filler that requires >500° F. for an extended time to expand the filler and cause a compressive force on the substrate. Mat supports without filler (non-intumescent type) also exist, but these supports are more expensive and harder to process to a minimum substrate holding pressure.
In another variation, an exhaust catalyst is supported by a fiber mat interwoven into a knitted wire mesh. This design is used to improve the thermal insulating value (i.e. reduce shell temperatures for heat management). However, this design is even more expensive than knitted wire mesh supports. In another prior art design, a corrugated metal inner liner is inserted into a pocket cut into a mat support. The corrugated metal is not on the outer part of the support, but on the inside. Its function is to prevent abrasion of the ceramic fiber mat in a space between two non-butted substrates and provide support for the catalyst. The purpose of the corrugation is to prevent sagging of the metal at high temperatures. However, the use of this last design is somewhat undesirable for catalyst support systems because the sandwiching of the corrugated metal greatly reduces its resiliency.
Accordingly, there exists a need in the prior art for improved catalyst supports that have a wider useful temperature range.
SUMMARY OF INVENTIONThe present invention overcomes the problems of the prior art by providing a combustion exhaust catalyst support for holding an exhaust catalyst in an exhaust system with a wide useful temperature range. The support of the invention includes a flexible refractory mat adapted to surround the exhaust catalyst and a metal foil having a plurality of protrusions disposed over the flexible refractory mat. The catalyst support is relatively inexpensive because forming protrusions in metal foil is an uncomplicated procedure especially when compared to forming knitted wire mesh. Moreover, because a refractory mat is also used, the support of the present invention has excellent thermally insulating properties. The catalyst support of the present invention is particularly useful for support of an automobile exhaust catalyst in an automobile exhaust system.
In another embodiment of the invention, an exhaust system in which a catalyst is held in place with the support of the invention is provided.
In yet another embodiment of the invention, methods for securing a catalyst to an exhaust system are provided.
Reference will now be made in detail to presently preferred compositions or embodiments and methods of the invention, which constitute the best modes of practicing the invention presently known to the inventors.
With reference to
Metal foil 12 may be made of any suitable metal which can withstand the temperatures and chemical environment of a combustion exhaust system. Suitable metals include, but are not limited to, stainless steels, nickel alloys, and cobalt alloys. More specific metals meeting the requirements for metal foil 12 are monels, hastelloys, inconels, 300 series stainless steels, and 400 series stainless steels. Inconel X750 is particularly useful for this application. Metal foil 10 may be made by a number of techniques known to one skilled in the art. For example, a sheet of metal foil is cut into a shape that when corrugated and wrapped in a hoop shape, will fit the inside of a converter shell (i.e., the housing that contains the exhaust catalyst.) The metal sheet is then corrugated in a crimping roller machine. Corrugations 24 in metal sheet 10 may be described as being approximately sinousoidal or triangular-shaped in cross section. However, any shape may be used so long as the resulting metal foil 12 have sufficient resilency (i.e., spring-like properties) that when compressed in a plane normal to refractory mat 16 it will tend to restore its original shape. Accordingly, metal foil 12 may have other types of protrusions instead of corrugations. For example, metal foil 12 may have square corrugations, circular corrugations, flattened shingle-like corrugations, or dimples. Finally, metal foil 10 will typically be from about 0.01 millimeters to about 0.5 millimeters thick. More preferably, metal foil 10 is from about 0.01 millimeters to about 0.2 millimeters thick.
Refractory mat 16 is preferably a ceramic fiber mat. Refractory mat 16 is made in the conventional way using a blend of ceramic fibers organic binders, and optionally tumescent materials (e.g. vermiculite). It is die-cut in the conventional way so that length d3 is slightly shorter than the corrugated metal shape by a distance two times d5. This shorter length is needed because the material is formed later to be toward the inside of the converter, so the periphery is smaller. The thickness of refractory mat 16 will typically be several millimeters. Preferably, the thickness of refractory mat 16 is from about 3 to 10 mm. More preferably, refractory mat 16 is from about 4 to 8 mm, and most preferably, refractory mat 16 is about 6 mm.
Still referring to
In another embodiment of the present invention, an exhaust system in which a catalyst is held in place by the catalyst support of the present invention is provided. This embodiment includes the support of the invention wrapped around an exhaust catalyst with the metal foil facing outward. This combination of support and catalyst is positioned in a metal tube which is adapted for inclusion in an exhaust system such as an automobile exhaust system. With reference to
With reference to
In another embodiment of the present invention, a method of supporting a combustion exhaust catalyst is provided. The method of this embodiment utilizes the catalyst support and mat set for above and is particularly useful for supporting an automobile exhaust catalyst in an automobile exhaust system. The method comprises placing a flexible refractory mat having a first surface and a second surface over a surface of an exhaust catalyst wherein the first surface is adjacent to the surface of the exhaust catalyst. Next, a metal foil having a plurality of protrusions is placed over the second surface of the refractory mat to form a catalyst-support combination. Alternatively, the metal foil may be placed over the second surface of the refractory mat prior to the placing of the refractory mat over the surface of the exhaust catalyst. In this latter variation, the metal foil and refractory mat are attached together as set forth above. The ends of the catalyst support can be held together with tape, organic glue, etc. to temporarily hold the support until the convertor is welded. The catalyst internal sub-assembly (i.e., the combination of the catalyst brick and the catalyst support) is then placed into a metal tube to form the catalytic converter in the conventional way (e.g. shoebox—sliding joints clamp and weld; clamshell—butted joints clamped and welded; stuffing a tube and swaging to reduce the outer diameter; tourniquet-one sliding joint, clamp and weld). The metal tube is adapted to be placed within a combustion exhaust system such as a vehicle exhaust system. The selection of the materials for the refractory mat and the metal foil as well as the shapes and thicknesses of these materials is the same as set forth above. Specifically, the plurality of protrusions within the metal foil comprise a plurality of ridges and grooves such that the metal foil is corrugated or alternatively, comprise a plurality of dimples.
A number of methods of placing the catalyst-support combination within the metal tube may be employed. For example, the catalyst-support combination may be slipped in the metal tube followed by swaging down on the metal tube until the catalyst-support combination is held in place (
Another method for placing the catalyst-support combination within the metal tube is the so-called “tourniquet method.” With reference to
While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.
Claims
1. A combustion exhaust catalyst support adapted to hold an exhaust catalyst in an exhaust system, the support comprising:
- a flexible refractory mat having a first surface and a second surface, the flexible refractory mat adapted to surround the exhaust catalyst with the first surface being adjacent to a surface of the exhaust catalyst; and
- a metal foil having a plurality of protrusions, the metal foil disposed over the second surface of the flexible refractory mat, wherein the metal foil is between about 0.01 millimeters to about 0.5 millimeters thick.
2. The support of claim 1 wherein the plurality of protrusions comprise a plurality of ridges and grooves such that the metal foil is corrugated.
3. The support of claim 1 wherein the plurality of protrusions comprise a plurality of dimples.
4. The support of claim 1 wherein the metal foil comprises a metal selected from the group consisting of stainless steels, nickel alloys, and cobalt alloys.
5. The support of claim 4 wherein the metal foil comprises a metal selected from the monels, hasteloys, inconels, 300 series stainless steels, and 400 series stainless steels.
6. The support of claim 1 wherein the metal foil is between about 0.01 millimeters to about 0.2 millimeters thick.
7. The support of claim 1 wherein the refractory mat comprises refractory ceramic fiber and a binder.
8. The support of claim 1 wherein the refractory mat is adapted to surround an exhaust catalyst comprising a refractory brick having a longitudinal axis, a surface substantially parallel to the longitudinal axis, a front surface, and a back surface, the refractory brick comprising a series of channels substantially parallel to the longitudinal axis which pass through the refractory brick.
9. The support of claim 8 wherein the first surface of the refractory mat is adjacent to the surface substantially parallel to the longitudinal axis.
10. The support of claim 9 wherein the refractory brick has a substantially circular or substantially elliptical cross-section.
11. The support of claim 1 wherein the metal foil includes a first end with a metal foil notch and a second end with a metal foil protrusion and the refractory mat includes a first end with a refractory mat notch and a second end with a refractory mat protrusion wherein the metal foil notch and metal foil protrusion are adapted to mate together and the refractory mat notch and refractory mat protrusion are adapted to mate together so that the support when placed around the exhaust catalyst is held in place.
12. An exhaust system comprising:
- an exhaust catalyst;
- a flexible refractory mat having a first surface and a second surface, the flexible refractory mat surrounding the exhaust catalyst with the first surface being adjacent to a surface of the exhaust catalyst; and
- a metal foil having a plurality of protrusions, the metal foil disposed over the second surface of the flexible refractory mat, wherein the metal foil is between about 0.01 millimeters to about 0.5 millimeters thick.
13. The exhaust system of claim 12 wherein the plurality of protrusions comprise a plurality of ridges and grooves such that the metal foil is corrugated.
14. The exhaust system of claim 12 wherein the plurality of protrusions comprise a plurality of dimples.
15. The exhaust system of claim 12 wherein the exhaust catalyst comprises a refractory brick having a longitudinal axis, a surface substantially parallel to the longitudinal axis, a front surface, and a back surface, the refractory brick comprising a series of channels substantially parallel to the longitudinal axis which pass through the refractory brick.
16. The exhaust system of claim 15 wherein the first surface of the refractory mat is adjacent to the surface substantially parallel to the longitudinal axis.
17. The exhaust system of claim 16 wherein the refractory brick has a substantially circular or substantially elliptical cross-section.
18. The exhaust system of claim 12 wherein the metal foil includes a first end with a metal foil notch and a second end with a metal foil protrusion and the refractory mat includes a first end with a refractory mat notch and a second end with a refractory mat protrusion wherein the metal foil notch and metal foil protrusion are adapted to mate together and the refractory mat notch and refractory mat protrusion are adapted to mate together so that the support when placed around the exhaust catalyst is held in place.
19. The exhaust system of claim 12 wherein the metal foil comprises a metal selected from the group consisting of stainless steels, nickel alloys, and cobalt alloys.
20. The exhaust system of claim 15 wherein the metal foil comprises a metal selected from the monels, hasteloys, inconels, 300 series stainless steels, and 400 series stainless steels.
21. The exhaust system of claim 12 wherein the refractory mat comprises refractory ceramic fiber and a binder.
22. A method of supporting an exhaust catalyst, the method comprising:
- placing a flexible refractory mat having a first surface and a second surface over a surface of an exhaust catalyst wherein the first surface is adjacent to the surface of the exhaust catalyst;
- placing a metal foil having a plurality of protrusions and a thickness of between about 0.01 millimeters to about 0.5 millimeters over the second surface of the refractory mat to form a catalyst-support combination; and
- securely placing catalyst-support combination within a metal tube, the metal tube adapted to be placed within an exhaust system.
23. The method of claim 22 wherein the plurality of protrusions comprise a plurality of ridges and grooves such that the metal foil is corrugated.
24. The method of claim 22 wherein the plurality of protrusions comprise a plurality of dimples.
25. The method of claim 22 wherein the catalyst-support combination is placed with a metal tube by sliding the catalyst-support combination in the metal tube and then swaging down on the metal tube until the catalyst-support combination is held in place.
26. The method of claim 22 wherein the metal tube has a pair of flanges and the catalyst-support combination is placed with a metal tube positioning the catalyst-support combination in the metal tube, compressing the metal tube so that the pair of flanges come in contact, and sealing the pair of flanges together.
27. The method of claim 22 wherein the metal tube comprises a first tube half and a second tube half so that the catalyst-support combination is placed in the metal tube by positioning the catalyst-support combination in a cavity formed by bringing the first tube half and the second tube half together.
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Type: Grant
Filed: Mar 18, 2004
Date of Patent: Jan 8, 2008
Patent Publication Number: 20050207947
Assignee: Ford Global Technologies, LLC (Dearborn, MI)
Inventor: Dave Weber (Toledo, OH)
Primary Examiner: Walter D. Griffin
Assistant Examiner: Frank C Campanell
Attorney: Brooks Kushman P.C.
Application Number: 10/708,687
International Classification: B01D 50/00 (20060101); B01J 8/02 (20060101);